Stents and other metallic implants can cause artifacts in magnetic resonance (MR) images due in part to distortions in the magnetic field. Distortions in the magnetic field are often caused by the shape of the stent that acts to partially shield a radio frequency (RF) field generated during the MR procedure. This shielding of the RF field is known as the Faraday Effect and is caused by structures, such as stents, that have a “Faraday Cage” configuration.
Generally, a Faraday Cage configuration prevents an RF field from penetrating to the interior of such a structure. Because stents are not ideal but only partial Faraday cages, a small percentage of the RF field still is able to penetrate to the interior, however not enough to give a reasonable visibility in the stent interior.
One approach to achieving the reasonable visibility would be to raise the energy of the RF field to such high levels that enough energy remains after passing through the partial stent shield for visualization. Unfortunately, taking this approach will cause the tissue of the body to be heated to unacceptable levels.